Process for forming porous nylon fiber rods

ABSTRACT

A PROCESS FOR PRODUCING POROUS NYLON FIBER RODS ADAPTABLE FOR USE AS A WICK IN FIBER POINT PENS INCLUDES THE FORMATION OF A STRAND OF TWISTED NYLON FIBERS AND THE AUTOGENEOUS BONDING OF ADJACENT NYLON FIBERS ALONG SELECTED CONTIGUOUS SURFACES TO PRODUCE A SERIES OF INTERCONNECTING LIQUID CONDUCTING PASSAGEWAYS WHEREBY THE RESULTING FIBER ROD HAS A DENSITY OF FROM 1.00 TO ABOUT 0.60 GM./CM3.

Aug. 10, 1971 KNUDSEN ETAL 3,598,674

PROCESS FOR FORMING POROUS NYLON FIBER RODS Filed Dec. 19, 1968 INVENTORS JOHN P. KNUDSEN 1 IIIII I II I IIII ROBERT E. MARTIN, WILLIAM C. MALLONEE ATTORNEY United States Patent O US. Cl. 156148 7 Claims ABSTRACT OF THE DISCLOSURE A process for producing porous nylon fiber rods adaptable for use as a wick in fiber point pens includes the formation of a strand of twisted nylon fibers and the autogeneous bonding of adjacent nylon fibers along selected contiguous surfaces to produce a series of interconnecting liquid conducting passageways whereby the resulting fiber rod has a density of from 1.00 to about 0.60 gm./cm.

BACKGROUND OF THE INVENTION (1) Field of the invention This invention relates to a process for the production of porous nylon fiber rods and, more specifically, to a process for forming porous nylon fiber rods by bonding touching nylon filaments together along their contiguous surfaces by contacting the filaments With a gas having been dissolved in an organic liquid carrier and by twisting the nylon filaments about its central axis so that upon removal of the gas from the nylon filaments, a porous bonded nylon rod is formed which is capable of wicking fluids at a desired rate of flow and of being machined to a fine point.

(2) Description of the prior art The use of fibrous materials as pen points is quite old in the art; however, the prior art pen points which are made from fibrous materials and are capable of wicking have unusually short lives and cannot withstand continued use when compared with metal tipped pen points or the like. Also, the wickability of the prior art fibrous pen points cannot easily be predetermined due to the 'variations in the length of fibers and of the binders used to bind the fibers together. As disclosed in US. Pat. 3,400,- 998, the fibers are held together by means of an adhesive binder which limits the control over rod porosity causing variations of the same along its length.

SUMMARY OF THE INVENTION In the process for forming porous nylon fiber rods from a plurality of nylon fibers, the fibers which may be either continuous or staple are submerged in an activating liquid or contacted with an activating gas. The fibers are twisted while being exposed to the activating liquid or gas and upon their removal are subjected to tension whereupon contiguous fibers are selectively bonded to each other along portions of their lengths. The bonding is completed by desorbing the activating liquid or gas from the nylon fibers which may be accomplished either by washing in hot water or by heat or the like.

The bonding of adjacent nylon fibers is controlled to produce a rod density, which is a measure of porosity, ranging from 1.00 to about 0.60 gm./cm. At high densities, the rod is substantially comprised of all nylon fibers whereas at low densities, the rod includes many void areas. Rod density is generally controlled by the degree of total fiber twist and the tension to which the rods are subjected during bonding. The nylon fibers comprising the fiber rod are bonded together autogenously, that is, no

3,598,674 Patented Aug. 10, 1971 outside agent remains in or around the fibers after the completion of the bonding process. Bonding occurs by contacting the fibers with a chemically active gaseous substance which upon being absorbed by the nylon fibers, causes a disruption in the interchain hydrogen bonding between adjacent amide groups within the nylon fibers. The covalent bonds within the polyamide chains are not broken or substantially altered. Upon removal of the gas from the polyamide filaments, the interchain hydrogen bonding between contiguous amides groups of adjacent nylon fibers are reformed as well as between the molecular chains comprising the body of the fiber. The gas may be mixed with other gases or may be dissolved in a nonionic organic liquid solvent which is chemically inert to the polyamide fibers and which serves as a carrier for the gas. The activating gases which may be combined with other inert gases or which may be dissolved in a suitable liquid solvent include hydrogen chloride, hydrogen bromide, boron trifiuoride, boron trichloride, sulfur trioxide, nitrogen trioxide and a combination of sulfur dioxide and chlorine. These and other related gases do not significantly degrade the fiber but, while in contact with the fiber, disrupt the interchain hydrogen bonds between adjacent amide groups as mentioned above. The non-ionizing liquid solvents in which the activating gases may be dissolved include acetone, ether, chloroform, carbon tetrachloride, benzene, pentane, heptane, trichlorofluromethane and other like organic liquids in which the particular gas re mains substantially non-ionized and which are substantially chemically inert to the polyamide fibers. The bonding liquid may be prepared by bubbling the gas through the organic liquid solvent carrier for a selected interval of time.

Therefore, an object of this invention is to provide a process for forming a porous nylon fiber rod which is capable of wicking ink and which is suitable for use as fiber points in felt pens or the like.

Another object of this invention is to provide a process for forming fiber points for fiber point pens having a density of from 1.00 to about 0.60 gm./cm.

Another object of this invention is to provide a process for forming fiber points for fiber point pens which are capable of enduring long use.

Another object of this invention is to provide a process for forming a porous nylon rod which is adaptable for use as a wicking element in fiber point pens.

More specific objects and advantages will be apparent to those skilled in the art from the following detailed description which illustrates and discloses but which is not intended to limit the scope of the invention.

DESCRIPTION OF THE DRAWINGS The figure is a schematic view of an apparatus capable of performing the process of this invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT Nylon yarns 10 are drawn from a plurality of bobbins 11 around guides 12 and into liquid 14. Each of the nylon yarns 10 is generally comprised of about 40 six denier continuous nylon fibers with the yarns having been twisted about 0.4 turn per inch. It is contemplated that from 16 to 20 yarns are to be used to produce a nylon fiber rod of from 65 to mils in diameter. Nylon yarns 10 having been drawn into liquid 14 remain apart by means of separation guides 15 and 16 for a period of approximately 10 seconds to allow for partial absorption by the fibers of the dissolved gas. The plurality of yarns 10 which form strand 19 are combined and twisted from 0.2 to 0.7 turn per inch by twist inducer 18. Strand 19 is then drawn through tension gate 20 whereupon tension gate 20 and nip rolls 21 and 22 cooperate to maintain the strand under approximately 50 grams of tension. The tension may be varied depending upon the desired porosity and may range as high as 1,000 grams. After a lag time of from about 60 to about 120 seconds while strand 19 is maintained under the desired tension, strand 19 is submerged in boiling water 23 at 100 C. whereupon the activating liquid including the dissolved gas is desorbed from the nylon fibers comprising strand 19. Strand 19 generally remains in Water bath 23 for a period of from to minutes whereupon it proceeds over roller 24 and through heating oven 25 to remove excess water clinging thereto. After removal from Wash bath 23, strand 19 does not have to be completely dried for fiber bonding has already oc curred. After partial or complete drying, strand 19 proceeds through nip rolls 21 and 22 Where the tension thereon is released. When desirable, cutter 26 may be installed in line to sever strand 19 into short lengths 27.

EXAMPLE I The activating liquid was prepared by bubbling dry hydrogen chloride gas through dry chloroform for approximately 4 minutes until the concentration was 0.15 N HCl. Continuous lengths of 18 yarns twisted at about 0.4 turn per inch of nylon fibers were withdrawn from their respective bobbins and were separatingly submerged in the activating liquid for approximately seconds. Each yarn contained about 140 continuous lengths of nylon fibers. The yarns were then combined and twisted at about 0.4 turn per inch while remaining in the activating liquid. After being twisted, the strand which was comprised of the yarns was withdrawn from the activating liquid and was passed through a tension gate whereupon the tension gate in cooperation with nip rollers maintained the strand under 50 grams of tension. After being maintained under the tension for about 90 seconds, the strand was then submerged in boiling water at 100 C. which desorbed the chloroform liquid carrier and the activating hydrogen chloride gas. The strand remained in the boiling water for a period of about 10 minutes whereupon the strand was withdrawn and was dried by means of a radiant heater for approximately 10 minutes. The resulting density was 0.80 gm./cm. The diameter of the fiber rod was 75 mils and had the characteristics of being tough while retaining the desired wickability.

EXAMPLE II The procedure as set forth in Example I was repeated with the exceptions that 16 yarns of nylon fibers were submerged in 500 ml. of bonding liquid. The resulting density was 0.82 gm./cm. which would indicate a slight increase in density as compared to Example I since the number of yarns comprising the strand was reduced by 2.

EXAMPLE III The procedure as set forth in Example I was repeated with the exceptions that the strand was submerged in 300 ml. of activating liquid and was allowed to remain therein for 10 seconds. The resulting density of the fiber rod was 0.79 gm./cm.

EXAMPLE IV The procedure as set forth in Example I was repeated with the exception that 16 yarns were submerged in 300 m1. of activating liquid for a period of 60 seconds. The strand was twisted at a rate of 0.2 twist per inch and after twisting was placed under 1,000 grams of tension between the tension gate and the nip rolls. The resulting density was 0.92 gm./cm. which would indicate an excess tension placed upon the strand.

EXAMPLE V The procedure as set forth in Example I was repeated with the exception that the yarns comprising the strand were placed into 300 ml. of bonding liquid for 10 seconds and the resulting strand was placed under 100 grams of tension. The resulting density was 0.81 gm./cm. It can 4 be seen that although tension under which the strand was placed was twice the tension of Example I, the amount of time the strand remained in the activating liquid was reduced by half resulting in fiber rods having substantially equal densities.

Many modifications of this invention may be made without departing from the scope and spirit thereof. It is contemplated that variations may be made in the type of activating gases dissolved in the non-ionic organic liquid; further, it is contemplated that the fibers may be contacted directly with the activating gas to provide the necessary bonding upon desorption of the gas. Also, it is contemplated that variations may be made in the density of the fiber rod without greatly altering the effectiveness of the process within the range of 1.00 to 0.60 gm./cm. therefore, applicants do not wish to be bound by the numbers except as they appear in the claims.

We claim:

1. A process for forming a porous nylon fiber rod comprising the steps of (a) contacting a plurality of nylon fibers with an activating fluid, said activating fluid being comprised of an organic liquid carrier which is inert to said nylon fibers and an activating gas having been dissolved in said liquid carrier, said activating gas being at least partially absorbed by said nylon fibers;

(b) twisting said fibers into a strand while said activating gas remains absorbed by said nylon fibers;

(c) placing said strand under tension to maintain contact between adjacent fibers;

(d) desorbing said activating gas from said nylon fibers by contacting said fibers with a medium heated to above the boiling point of said organic liquid carrier While said strand remains under said tension to bond autogenously adjacent nylon fibers along selected contiguous fiber surfaces to provide a rod with interconnecting liquid conducting passageways at a density of from about 1.00 to about 0.60 g./cm.

2. The process of claim 1 wherein said nylon fibers are of continuous lengths.

3. The process of claim 2 wherein said activating gas was desorbed from said nylon fibers by submerging said fibers in water heated to a temperature above the boiling point of said organic liquid carrier.

4. The process of claim 3 wherein said continuous lengths of nylon are drawn from a plurality of bobbins in the form of yarns with each of said yarns being comprised of a plurality of nylon fibers.

5. The process of claim 4 wherein the diameter of said fiber rod is from about 65 mils to about mils.

6. The process of claim 5 wherein said fiber rod is comprised of about 6 denier fibers.

7. The process of claim 6 wherein each of said yarns is twisted at a rate of about 0.4 turn per inch and said plurality of yarns are twisted to form said fiber rod at a rate of about 0.4 turn per inch.

References Cited UNITED STATES PATENTS 3,079,978 3/1963 Cobb et a1 156-307X 3,080,611 3/1963 Jarrett et al 156200X 3,111,702 11/1963 Berger 40l198X 3,151,011 9/1964 Troelernan et al. 156l80 3,190,294 6/1965 Dunlap 401-198 3,232,805 2/1966 Touey et al. 156-180 3,400,998 9/1968 Daugherty et al 40'l198 3,467,564 9/1969 Daugherty et al. l56-180X 3,516,900 6/ 1970 Mallonee et al 156306X 3,536,556 10/1970 Stevenson 156-166 CARL D. QUARFORTH, Primary Examiner G. G. SOLYST, Assistant Examiner US. Cl. X.R. l56--180, 306, 441 

